Field of the Invention
The present invention relates generally to a method for preventing abrasion of video heads in a video tape recorder. More specifically, the present invention relates to a method for eliminating friction between video heads and a recording medium in a time-lapse video tape recorder by loosening the tension of the recording medium when the head drum keeps rotating and the recording medium is maintained in its loaded state during an intermittent recording pause period.
Unlike an ordinary continuous video tape recorder which records every frame of video signals, a time-lapse video tape recorder intermittently records video signals from several video cameras on a magnetic tape at a pre-selected regular time interval. During the recording, the magnetic tape is moved and stopped, repeatedly. The time-lapse video tape recorder is often used in various areas requiring long-time recording, such as, a security monitoring system in banks and museums.
FIG. 1 shows a block diagram of a general time-lapse video tape recorder. As shown in therein, a time-lapse video tape recorder generally includes an AID converter 100 which converts an analog video signal from an external video camera into a digital data stream, a buffer memory 201 in which the digital video data are stored temporarily, a field memory 202 in which the digital video data from the buffer memory 201 are stored before they are recorded on a magnetic tape, a D/A converter 300 which converts the digital video data in the field memory 202 into an analog video signal, a recording unit 400 which records the analog video signal on the magnetic tape, and a controller 500 which controls writing/reading intervals of video signal received from the external video cameras to/from the memories 201 and 202 according to a user input from an input unit 600.
The time-lapse video tape recorder further comprises a loading motor 401, a drum motor 402, and a capstan motor 403, and the recording unit 400 comprises a signal processing unit which processes the video signal for recording, and mechanical elements, shown in FIGS. 2 to 5.
The loading motor 401 moves a loading post 1 to load/unload a magnetic tape TP. The drum motor 402 rotates a head drum 3 on which a video head 2 is mounted to record/reproduce the video signal on the magnetic tape TP. The capstan motor 403 rotates a capstan shaft 4 to move the tape TP at a designated tape running speed. An idler gear 6 transmits the rotating force of the capstan motor 403 to either a supply reel 7 or a take-up reel 8 to wind the tape TP loosened due to the forward or reverse movement of the tape TP.
In the time-lapse video tape recorders configured as above, the tape TP is maintained in the loading state and the head drum 3 is rotating in a recording pause period. Depending on the length of the recording pause period, the tape TP can be unloaded or the rotation of the head drum 3 can be suspended temporarily during the recording pause period. The method for unloading the tape TP or stopping rotation of the head drum 3 is described below in more detail.
The video signal received from an external video camera is converted into a stream of digital video frames by the A/D converter 100 and then stored in the field memory 202 via the buffer memory 201. The video frames in the buffer memory 202, which are received in real time, are selected intermittently at the predetermined time interval between frames, and the selected frames are stored in the field memory 202.
When the number of the video frames stored in the field memory 202 becomes equal to 150 frames (the storage capacity of the field memory 202), the stored video frames are read out and, in turn, converted into analog video signals. These analog video signals are recorded on the tape TP in the recording unit 400 while the tape TI moves in the forward direction.
The video signal output from the external video camera is continually stored in the buffer memory 201 during the recording of the stored video frames on the tape TP. When the recording of the 150 frames stored in the field memory 202 is completed, new 150 frames stored in the buffer memory 201 are transferred to the empty field memory 202 at the frame extraction ratio corresponding to a selection interval of video frames. The recording unit 400 is maintained in an idle state until the field memory 202 becomes full again. This way, the recording unit 400 alternates between the recording mode and the recording pause mode.
When a user inputs a total recording time desired, a recording pause period is calculated by the controller 500 in consideration of the storage capacity of the field (e.g., 3 minutes), the recording unit 400 operates in an alternating mode. In the alternative mode, the tape TP is unloaded and the rotation of the head drum 3 is stopped during a pause period of the alternative mode, as shown in FIG. 3, and then the tape TP is loaded again and the rotation of the head drum 3 is resumed during a recording period of the alternative mode, as shown in FIG. 2. Otherwise, the recording unit 400 operates in a mode where the tape TP is loaded and the head drum 3 rotates all the time regardless of the recording or non-recording period.
In the above-described recording/reproduction methods, however, there exist periods in which the tape TP is maintained in its loading state and the head drum 3 rotates even though no recording occurs during these periods. During such periods, video heads constantly contact the tape TP. For example, in the alternating mode, when the recording pause period is shorter than 3 minutes, the video heads contact the tape TP. As a result, the video heads are easily worn out due to the friction between the tape TP and the rotating head drum 3 and/or heads 2. Consequently, the video signal is recorded on the tape TP in low quality, and the lifespan of the magnetic tape TP is considerably shortened.
Accordingly, an object of the present invention is to solve the above mentioned problems and other disadvantages of the conventional methods.
Another object of the present invention is to provide a method for eliminating friction between a video head and a recording tape in a time-lapse video tape recorder by loosening the tension of the recording tape while still in the loaded state during a recording/reproduction pause period.
Briefly described, the present invention is directed to a method for a recording/reproducing apparatus during a non-recording period in which a recording medium is in a loaded position and a head drum of the recording/reproducing apparatus is rotating, wherein the recording/reproduction apparatus further includes a video head, a supply-reel, a take-up reel, and an idler arm movable between the supply-reel and the take-up reel, the method comprising the step of eliminating friction between the recording medium and at least one of the video head and the head drum.
Furthermore, a method for preventing abrasion of video heads of a recording/reproducing apparatus, according to the present invention includes the steps of determining whether or not recording in the recording/reproducing apparatus has paused in an intermittent recording mode; and loosening tension of a loaded recording medium based on the determination result.
Moreover, a method for a recording/reproducing apparatus having a memory for storing video data therein, a video head for recording and reproducing data on and from a recording medium, and a head drum, according to the present invention includes the steps of reproducing video signals recorded on the recording medium; storing the reproducing video signals in the memory; determining whether the memory is fill; and eliminating friction between the recording medium and at least one of the video head and the head drum based on a result from the determining step.
The present invention takes the effect of preventing abrasion of the video heads and the recording medium (e.g., magnetic tape) in case where the recording medium is maintained in its loading state and the head drum keeps rotating in an intermittent recording mode.
The above objectives, features, and advantages of the present invention will become apparent from the following detailed description of illustrative embodiments thereof to read in conjunction with the accompanying drawings.